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Rated temperature TR 25 °CDissipation factor (in air) δth approx. 4 mW/K
Thermal cooling time constant (in air) τc approx. 15 s
Heat capacity Cth approx. 60 mJ/K
Electrical specification and ordering codes
R25
ΩNo. of R/T
characteristic
B25/100
K
Ordering code
+ = Resistance tolerance
F = ±1%
H = ±3%
J = ±5%
2.2 k 1008 3560 ±1.5% B57891S0222+008
5 k 2003 3980 ±1% B57891S0502+008
10 k 4901 3950 ±1% B57891S0103+008
20 k 2904 4300 ±1% B57891S0203+008
100 k 4003 4450 ±1% B57891S0104+008
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 2 of 26Please read Cautions and warnings andImportant notes at the end of this document.
Reliability data
Test Standard Test conditions ∆R25/R25
(typical)
Remarks
Storage in
dry heat
IEC
60068-2-2
Storage at upper
category temperature
T: 155 °Ct: 1000 h
< 3% No visible
damage
Storage in damp
heat, steady state
IEC
60068-2-78
Temperature of air: 40 °CRelative humidity of air: 93%
Duration: 56 days
< 1% No visible
damage
Rapid temperature
cycling
IEC
60068-2-14
Lower test temperature: 55 °CUpper test temperature: 155 °CNumber of cycles: 100
< 2% No visible
damage
Endurance Pmax: 200 mW
t: 1000 h
< 3% No visible
damage
Long-term stability
(empirical value)
Temperature: 70 °Ct: 10000 h
< 3% No visible
damage
Note
Contact of NTC thermistors with any liquids and solvents shall be prevented. It must beensured that no water enters the NTC thermistors (e.g. through plug terminals).Avoid dewing and condensation unless thermistor is specified for these conditions.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 3 of 26Please read Cautions and warnings andImportant notes at the end of this document.
R/T characteristics
R/T No. 1008 2003 2904
T (°C) B25/100 = 3560 K B25/100 = 3980 K B25/100 = 4300 K
- Temperature min Tsmin 100 °C 150 °C- Temperature max Tsmax 150 °C 200 °C- Time tsmin to tsmax 60 ... 120 s 60 ... 180 s
Average ramp-up rate Tsmax to Tp 3 °C/ s max. 3 °C/ s max.
Liquidous temperature TL 183 °C 217 °CTime at liquidous tL 60 ... 150 s 60 ... 150 s
Peak package body temperature Tp1) 220 °C ... 235 °C2) 245 °C ... 260 °C2)
Time (tP)3) within 5 °C of specified
classification temperature (Tc)20 s3) 30 s3)
Average ramp-down rate Tp to Tsmax 6 °C/ s max. 6 °C/ s max.
Time 25 °C to peak temperature maximum 6 min maximum 8 min
1) Tolerance for peak profile temperature (TP) is defined as a supplier minimum and a user maximum.
2) Depending on package thickness. For details please refer to JEDEC J-STD-020D.
3) Tolerance for time at peak profile temperature (tP) is defined as a supplier minimum and a user maximum.
Note: All temperatures refer to topside of the package, measured on the package body surface.
Number of reflow cycles: 3
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 17 of 26Please read Cautions and warnings andImportant notes at the end of this document.
Solder joint profiles for silver/nickel/tin terminations
1.3.3 Recommended geometry of solder pads
Recommended maximum dimensions (mm)
Case size
inch/mm
A B C
0402/1005 0.6 0.6 1.7
0603/1608 1.0 1.0 3.0
0805/2012 1.3 1.2 3.4
1206/3216 1.8 1.2 4.5
1.3.4 Notes
Iron soldering should be avoided, hot air methods are recommended for repair purposes.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 18 of 26Please read Cautions and warnings andImportant notes at the end of this document.
2 Conductive adhesion
An alternative to soldering is the gluing of thermistors with conductive adhesives. The benefit of
this method is that it involves no thermal stress. The adhesives used must be chemically inert.
3 Clamp contacting
Pressure contacting by means of clamps is particularly suitable for applications involving frequent
switching and high turn-on powers.
4 Robustness of terminations (leaded types)
The leads meet the requirements of IEC 60068-2-21. They may not be bent closer than 4 mm
from the solder joint on the thermistor body or from the point at which they leave the feed-
throughs. During bending, any mechanical stress at the outlet of the leads must be removed. The
bending radius should be at least 0.75 mm.
Tensile strength: Test Ua1:
Leads ∅ ≤0.25 mm = 1.0 N
0.25 < ∅ ≤0.35 mm = 2.5 N
0.35 < ∅ ≤0.50 mm = 5.0 N
0.50 < ∅ ≤0.80 mm = 10.0 N
0.80 < ∅ ≤1.25 mm = 20.0 N
Bending strength: Test Ub:
Two 90°-bends in opposite directions at a weight of 0.25 kg.
Torsional strength: Test Uc: severity 2
The lead is bent by 90° at a distance of 6 to 6.5 mm from the thermistor body.
The bending radius of the leads should be approx. 0.75 mm. Two torsions of
180° each (severity 2).
When subjecting leads to mechanical stress, the following should be observed:
Tensile stress on leads
During mounting and operation tensile forces on the leads are to be avoided.
Bending of leads
Bending of the leads directly on the thermistor body is not permissible.
A lead may be bent at a minimum distance of twice the wire's diameter +2 mm from the solder
joint on the thermistor body. During bending the wire must be mechanically relieved at its outlet.
The bending radius should be at least 0.75 mm.
Twisting of leads
The twisting (torsion) by 180° of a lead bent by 90° is permissible at 6 mm from the bottom of the
thermistor body.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 19 of 26Please read Cautions and warnings andImportant notes at the end of this document.
5 Sealing and potting
When thermistors are sealed, potted or overmolded, there must be no mechanical stress caused
by thermal expansion during the production process (curing / overmolding process) and during
later operation. The upper category temperature of the thermistor must not be exceeded. Ensure
that the materials used (sealing / potting compound and plastic material) are chemically neutral.
6 Cleaning
Washing processes may damage the product due to the possible static or cyclic mechanical
loads (e.g. ultrasonic cleaning). They may cause cracks to develop on the product and its parts,
which might lead to reduced reliability or lifetime.
7 Storage
In order to maintain their solderability, thermistors must be stored in a non-corrosive atmosphere.
Humidity, temperature and container materials are critical factors.
Do not store SMDs where they are exposed to heat or direct sunlight. Otherwise, the packing ma-
terial may be deformed or SMDs may stick together, causing problems during mounting. After
opening the factory seals, such as polyvinyl-sealed packages, use the SMDs as soon as possible.
The components should be left in the original packing. Touching the metallization of unsoldered
thermistors may change their soldering properties.
Storage temperature: 25 °C up to 45 °C
Relative humidity (without condensation): ≤75% annual mean
<95%, maximum 30 days per annum
Solder the thermistors listed in this data book after shipment from EPCOS within the time speci-
fied:
SMDs with nickel barrier termination: 12 months
SMDs with AgPd termination: 6 months
Leaded components: 24 months
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 20 of 26Please read Cautions and warnings andImportant notes at the end of this document.
8 Placement and orientation of SMD NTC thermistors on PCB
a) Component placement
It is recommended that the PC board
should be held by means of some
adequate supporting pins such as
shown left to prevent the SMDs from
being damaged or cracked.
b) Cracks
When placing a component near an
area which is apt to bend or a grid
groove on the PC board, it is advisable
to have both electrodes subjected to
uniform stress, or to position the
component's electrodes at right angles
to the grid groove or bending line (see
c) Component orientation).
c) Component orientation
Choose a mounting position that
minimizes the stress imposed on the
chip during flexing or bending of the
board.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 21 of 26Please read Cautions and warnings andImportant notes at the end of this document.
Cautions and warnings
See "Important notes".
Storage
Store thermistors only in original packaging. Do not open the package prior to storage.Storage conditions in original packaging: storage temperature 25 °C ... +45 °C, relativehumidity ≤75% annual mean, <95% maximum 30 days per annum, dew precipitation isinadmissible.Do not store thermistors where they are exposed to heat or direct sunlight. Otherwise, thepacking material may be deformed or components may stick together, causing problems duringmounting.Avoid contamination of thermistor surface during storage, handling and processing.Avoid storage of thermistors in harmful environments like corrosive gases (SOx, Cl etc).Use the components as soon as possible after opening the factory seals, i.e. thepolyvinyl-sealed packages.Solder thermistors within the time specified after shipment from EPCOS.
For leaded components this is 24 months, for SMD components with nickel barrier termination
12 months, for SMD components with AgPd termination 6 months.
Handling
NTC thermistors must not be dropped. Chip-offs or any other damage must not be causedduring handling of NTCs.Do not touch components with bare hands. Gloves are recommended.Avoid contamination of thermistor surface during handling.Washing processes may damage the product due to the possible static or cyclic mechanicalloads (e.g. ultrasonic cleaning). They may cause cracks to develop on the product and its parts,which might lead to reduced reliability or lifetime.
Bending / twisting leads
A lead (wire) may be bent at a minimum distance of twice the wire’s diameter plus 4 mm fromthe component head or housing. When bending ensure the wire is mechanically relieved at thecomponent head or housing. The bending radius should be at least 0.75 mm.Twisting (torsion) by 180° of a lead bent by 90° is permissible at 6 mm from the bottom of thethermistor body.
Soldering
Use resin-type flux or non-activated flux.Insufficient preheating may cause ceramic cracks.Rapid cooling by dipping in solvent is not recommended.Complete removal of flux is recommended.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 22 of 26Please read Cautions and warnings andImportant notes at the end of this document.
Mounting
Ensure that no thermo-mechanical stress occurs due to production processes (curing orovermolding processes) when thermistors are sealed, potted or overmolded or during theirsubsequent operation. The maximum temperature of the thermistor must not be exceeded.Ensure that the materials used (sealing/potting compound and plastic material) are chemicallyneutral.Electrodes/contacts must not be scratched or damaged before/during/after the mountingprocess.Contacts and housing used for assembly with the thermistor must be clean before mounting.Ensure that adjacent materials are designed for operation at temperatures comparable to thesurface temperature of the thermistor. Be sure that surrounding parts and materials canwithstand the temperature.Avoid contamination of the thermistor surface during processing.The connections of sensors (e.g. cable end, wire end, plug terminal) may only be exposed toan environment with normal atmospheric conditions.Tensile forces on cables or leads must be avoided during mounting and operation.Bending or twisting of cables or leads directly on the thermistor body is not permissible.Avoid using chemical substances as mounting aids. It must be ensured that no water or otherliquids enter the NTC thermistors (e.g. through plug terminals). In particular, water basedsubstances (e.g. soap suds) must not be used as mounting aids for sensors.
Operation
Use thermistors only within the specified operating temperature range.Use thermistors only within the specified power range.Environmental conditions must not harm the thermistors. Only use the thermistors undernormal atmospheric conditions or within the specified conditions.Contact of NTC thermistors with any liquids and solvents shall be prevented. It must beensured that no water enters the NTC thermistors (e.g. through plug terminals). Formeasurement purposes (checking the specified resistance vs. temperature), the componentmust not be immersed in water but in suitable liquids (e.g. Galden).Avoid dewing and condensation unless thermistor is specified for these conditions.Bending or twisting of cables and/or wires is not permissible during operation of the sensor inthe application.Be sure to provide an appropriate fail-safe function to prevent secondary product damagecaused by malfunction.
This listing does not claim to be complete, but merely reflects the experience of EPCOS AG.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 23 of 26Please read Cautions and warnings andImportant notes at the end of this document.
Symbols and terms
Symbol English German
A Area Fläche
AWG American Wire Gauge Amerikanische Norm für Drahtquerschnitte
B B value B-Wert
B25/100 B value determined by resistance
measurement at 25 °C and 100 °CB-Wert, ermittelt durch Widerstands-
messungen bei 25 °C und 100 °C
Cth Heat capacitance Wärmekapazität
I Current Strom
N Number (integer) Anzahl (ganzzahliger Wert)
P25 Maximum power at 25 °C Maximale Leistung bei 25 °CPdiss Power dissipation Verlustleistung
Pel Electrical power Elektrische Leistung
Pmax Maximum power within stated
temperature range
Maximale Leistung im
angegebenenTemperaturbereich
∆RB/RB Resistance tolerance caused by
spread of B value
Widerstandstoleranz, die durch die
Streuung des B-Wertes verursacht wird
Rins Insulation resistance Isolationswiderstand
RP Parallel resistance Parallelwiderstand
RR Rated resistance Nennwiderstand
∆RR/RR Resistance tolerance Widerstandstoleranz
RS Series resistance Serienwiderstand
RT Resistance at temperature T
(e.g. R25 = resistance at 25 °C)
Widerstand bei Temperatur T
(z.B. R25 = Widerstand bei 25 °C)
T Temperature Temperatur
∆T Temperature tolerance Temperaturtoleranz
t Time Zeit
TA Ambient temperature Umgebungstemperatur
Tmax Upper category temperature Obere Grenztemperatur
(Kategorietemperatur)
Tmin Lower category temperature Untere Grenztemperatur
(Kategorietemperatur)
Top Operating temperature Betriebstemperatur
TR Rated temperature Nenntemperatur
Tsurf Surface temperature Oberflächentemperatur
V Voltage Spannung
Vins Insulation test voltage Isolationsprüfspannung
Vop Operating voltage Betriebsspannung
Vtest Test voltage Prüfspannung
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 24 of 26Please read Cautions and warnings andImportant notes at the end of this document.
Symbol English German
α Temperature coefficient Temperaturkoeffizient
∆ Tolerance, change Toleranz, Änderung
δth Dissipation factor Wärmeleitwert
τc Thermal cooling time constant Thermische Abkühlzeitkonstante